In general, a gas turbine, a steam turbine, and the like include a shaft seal mechanism provided around a rotating shaft in order to reduce the amount of gas leaking from a high pressure side to a low pressure side. An example of the shaft seal mechanism is a mechanism called a leaf seal and including flat thin plates (called “leaves”) arranged in multiple layers in a circumferential direction of the rotating shaft and having a predetermined width dimension in the axial direction of the rotating shaft (see, for example, PTL 1, which is hereby incorporated by reference herein in its entirety). A leaf seal housing is also known as a cover for the leaf seal. The leaf seal housing is also called a leaf seal casing.